Preheat oven to 375 °F (190 °C). In a large bowl combine flour, baking soda and salt; set aside. In a large mixing bowl, cream the butter, shortening, and sugars until light and fluffy. Add egg and vanilla, beating until well blended. Stir in flour mixture until just mixed. Fold in morsels and walnuts. Drop by tablespoonfuls 2-inches apart onto baking sheet and bake for 10 to 12 minutes or until lightly browned. Turn baking sheet around after 6 minutes to ensure even browning. Transfer cookies to wire rack to cool completely. Store in tightly covered container at room temperature.